Effect of distance from target on hypopituitarism after stereotactic radiosurgery for pituitary adenomas

Introduction Delayed hypopituitarism is the most common complication after stereotactic radiosurgery (SRS) for pituitary adenomas. The aim of this study was to investigate the relationship between the distance from the hypothalamic-pituitary axis to the treatment target and anterior pituitary function preservation after SRS. Methods Between 2007 and 2020, consecutive adult patients who underwent single-session SRS for non-functioning or hormone-secreting pituitary adenomas with >= 6 months of follow-up were included. Distance measurements between hypothalamic-pituitary axis structures and the SRS target volume were quantified on MRI. The primary outcome was anterior pituitary function preservation. Outcomes were compared using multivariable regression and area under the receiver operator characteristic curve (AUROC) analyses. Results The study cohort comprised 224 patients, who were categorized by preservation (n = 168) and no preservation (n = 56) of anterior pituitary function after SRS. The mean and median clinical follow-up durations were 53.7 (38.0) and 46.0 (17.0-75.0) months, respectively. Independent predictors of anterior pituitary function preservation were a greater distance between the center of the pituitary gland and center of the SRS target [OR 1.101 (1.000-1.213), p = 0.050], and a shorter clinical follow-up duration [OR 0.985 (0.977-0.993), p < 0.0001]. The adjusted AUROC for the distance from the center of the pituitary gland and center of the SRS target in predicting anterior pituitary function preservation was 0.595. The sensitivity, specificity, positive predictive value and negative predictive value in predicting anterior pituitary function preservation at the optimal cut-off distance of 15 mm were 30.0, 88.0, 89.9 and 26.2%, respectively. Conclusions Greater distance between the normal pituitary gland and the SRS target is associated with anterior pituitary function preservation and increasing this distance should be a goal of adenoma resection. Larger prospective, multi-center studies are necessary to corroborate this finding and establish the effects of distance on hypopituitarism after SRS for pituitary adenomas.